There are two different treatment modes for NSCLC patients who failed to epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) after initially responding to EGFR-TKI. One is EGFR-TKI combined with chemotherapy and the other is chemotherapy followed by EGFR-TKI. It is unclear which one is more suitable to this group of lung cancer patients. So this phase Ⅱclinical trial is designed to compare the efficiency and safety of these two different treatment modes.